Lecture 14 10/23/24 Flashcards

1
Q

What are the characteristics of Rhodococcus equi?

A

-gram-pos pleomorphic rods
-Chinese character formations
-facultative intracellular pathogen
-soil organism
-harbored in intestinal tract of adult herbivores
-inhaled or ingested
-seen in 1-6 month old foals
-insidious disease (gradual)

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2
Q

What are the clinical manifestations of Rhodococcus equi?

A

-chronic suppurative pneumonia
-anorexia
-lethargy
-fever
-nasal discharge +/- cough
-tachypnea
-dyspnea
-nostril flaring
-abdominal breathing

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3
Q

What are the extra-pulmonary manifestations of Rhodococcus equi?

A

*intestinal manifestations:
-possibly subclinical
-ulcerative colitis
-typhylitis
-suppurative inflammation of colonic/mesenteric lymph nodes
*polysynovitis
*panophthalmitis
*guttural pouch empyema
*sinusitis
*pericarditis
*hepatic and renal abscessation

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4
Q

What findings are seen on bloodwork with Rhodococcus equi?

A

-hyperfibrinogenemia
-neutrophilic leukocytosis +/- monocytosis

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5
Q

What findings are seen on radiographs with Rhodococcus equi?

A

-alveolar pattern
-regional consolidation and/or abscessation

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6
Q

Which methods are used to diagnose Rhodococcus equi?

A

-TTW with cytology and bacterial culture
-PCR

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7
Q

What are the characteristics of antibiotic treatment for Rhodococcus equi?

A

-erythromycin + rifampin
-given for 4-10 weeks
-can use azithromycin or clarithromycin

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8
Q

What are the side effects of antibiotic treatment of Rhodococcus equi?

A

-idiosyncratic hyperthermia and tachypnea
-self limiting fecal softening
-Clostridium difficile enterocolitis in mares exposed to the macrolides

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9
Q

What are the supportive treatments for Rhodococcus equi?

A

-oxygen support
-hyperbaric oxygen
-IV fluids
-nutrition support
-monitoring of fibrinogen
-radiographs/ultrasound for monitoring

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10
Q

What is the prognosis of Rhodococcus equi infection?

A

-treatment is very successful
-poorer prognosis with extra-pulmonary manifestations of disease
-decreased chance of racing as an adult, but performance in those racing not reduced significantly

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11
Q

What are the surveillance strategies for Rhodococcus equi?

A

-daily rectal temps
-fibrinogen levels measured every 2 weeks
-WBC count measured every 2 weeks
-ultrasound every 2 weeks (detects peripheral lesions only)

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12
Q

How is Rhodococcus equi controlled?

A

-avoid high animal density
-avoid sandy/dusty soils and manure laden areas
-pasture rotation
-plant or irrigate dusty paddocks/pastures
-surveillance strategies
-hyperimmune plasma
-prophylactic administration of azithromycin

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13
Q

What are the terms used for moderate/severe and mild equine asthma?

A

moderate/severe: recurrent airway obstruction/RAO
mild: inflammatory airway disease/IAD

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14
Q

What are the characteristics of equine asthma?

A

-naturally occurring
-periods of reversible airway inflammation

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15
Q

What causes the clinical signs of equine asthma?

A

-neutrophil accumulation
-mucus production
-bronchospasm

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16
Q

What is the impact of equine asthma on the lungs?

A

-decreased compliance
-increased resistance
-increased work of breathing
-arterial hypoxia

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17
Q

What is the epidemiology of equine asthma?

A

-seen in horses that are stalled and fed hay
-increased incidence with age
-familial tendency

18
Q

What is the pathophysiology of equine asthma?

A

-inhalation of dusts and molds increases IL-8 production
-neutrophil accumulation leads to small airway obstruction
-mucus accumulation, bronchospasm, and inflammatory changes in airway walls increase small airway obstruction
-obstruction leads to V/Q mismatch (poor vent., normal perfusion)
-inefficient gas exchange leads to hypoxia
-horses increase resp rate to compensate, but tidal vol. remains the same
-abnormal breathing pattern occurs

19
Q

What is the typical history of a horse with equine asthma?

A

-stalled and eating hay
-coughing
-decreased exercise tolerance
-prolonged recovery from exercise
-nasal discharge
-resp distress

20
Q

What are the clinical signs of equine asthma?

A

-cough
-nasal discharge
-flared nostrils
-increased resp rate
-rapid inspiration and forced prolonged expiration
-weight loss
-increased effort of breathing
-heave line

21
Q

What can be heard during auscultation in horses with asthma?

A

-can be quiet
-increased breath sounds
-crackles and wheezes
-tracheal rattle

22
Q

What findings can be found on arterial blood gas in horses with asthma?

A

-chronic respiratory acidosis
-hypoxemia
*depends on magnitude of resp compromise

23
Q

What is the primary finding on BAL in equine asthma?

A

non-degenerate neutrophilic inflammation

24
Q

What are the findings on radiographs in equine asthma?

A

-increased bronchovascular and interstitial changes
-lung hyperinflation

25
Q

What is an atropine or buscopan test?

A

short lived broncho-dilator administration to determine if patient symptoms improve
*associated with development of ileus

26
Q

What are the options for allergy testing in horses?

A

-serum
-intradermal

27
Q

What are principles of equine asthma control?

A

-environmental control
-reduce inflammation
-relieve resp distress

28
Q

Which components of environmental control are important for equine asthma?

A

-house horses 100% outdoors
-bedding
-diet

29
Q

How can inflammation be reduced in equine asthma?

A

-NSAIDs
-inhaled or systemic corticosteroids

30
Q

Which systemic corticosteroids are used in equine asthma?

A

-dexamethasone: short acting and easily withdrawn
-prednisolone: less side effects
-triamcinolone: long acting

31
Q

What are the characteristics of systemic corticosteroids for equine asthma?

A

-oral or injectable
-more side effects since acting systemically
-lowest possible dose is used
-help to prevent airway remodeling

32
Q

Which inhaled corticosteroids are used in equine asthma?

A

-beclomethasone
-fluticasone

33
Q

What are the characteristics of inhaled corticosteroids for equine asthma?

A

-use metered dose inhalers
-not systemic, less side effects
-not for initial or emergency use; require animal to take deep breaths

34
Q

Which classes of bronchodilators are used to relieve resp distress?

A

-anticholinergics
-beta-2 adrenergic agonists
-methylxanthines

35
Q

What are the characteristics of atropine?

A

-anticholinergic
-IV
-ileus and excitement with repeat doses

36
Q

What are the characteristics of ipratropium?

A

-anticholinergic
-inhalation
-no side effects

37
Q

What are the characteristics of clenbuterol?

A

-beta-2 agonist
-given oral or IV
-only FDA approved bronchodilator for horses

38
Q

What are the characteristics of albuterol?

A

-beta-2 agonist
-given oral or IV
-not well absorbed orally in horses

39
Q

What are the characteristics of theophylline?

A

-methylxanthine
-oral
-erratic absorption and narrow therapeutic index

40
Q

What are other potential treatments for equine asthma?

A

-mucolytic drugs
-antihistamines

41
Q

What are the steps to prevention of equine asthma?

A

-provide clean, well ventilated housing
-properly treat and manage resp disease

42
Q

What is the prognosis of equine asthma?

A

-dependent on disease stage
-unknown if chronic airway remodeling can be reversed
-important to prevent recurrence of airway inflammation
-expensive to maintain lung health